DE1057003B - Process for the production of ferrites - Google Patents

Description

Process for the production of ferrites. and high-frequency technology under the name of ferrites used iron spins, Crystal compounds from iron (III) oxide and suitable oxides of divalent metals, such as in particular nickel and zinc oxide, possibly also copper, cadmium, magnesium, Manganese, lead and cobalt oxides are made by mixing very mixtures pure active iron (III) oxide or oxide hydrate with oxides, hydroxides, carbonates or salts of other volatile acids of the divalent metals, their type and amount The ferrites are adapted to the desired properties, initially longer Time at about 800 ° C, heated, cooled, wet ground, dried and finally Glows in pure oxygen for a few hours at temperatures of around 1200 to 1400 ° C. Attempts have also been made to achieve a more intimate mixing of the oxides through common Precipitation of trivalent iron and divalent metal ions from mixed salt solutions to achieve with alkalis in order to thereby the formation of more uniform, well crystallized To facilitate spinels during subsequent annealing. However, this path failed because the alkali is not sufficiently washed out of the voluminous precipitates is, so that residues thereof go into the end products and deteriorate their properties.

It has now been found that high-quality ferrites of the type mentioned can produce in a technically particularly advantageous manner that one mixed aqueous solution of ferrous salts and salts of other suitable divalent salts Metals with an insufficient amount for the complete precipitation of the metal ions Amount of a basic precipitant, e.g. B. an alkali hydroxide or carbonate solution, added, the mixture is a preferably coarsely crushed metal alloy, the iron and the other metals according to type and amount according to the metal ions of the starting solution or the precipitate contains, and an oxidizing agent, preferably air or an aromatic nitro compound, in particular nitrobenzene, adds, the precipitate, an intimate mixture of iron (III) oxydhy brat and the divalent metal hydroxides or from already finished, finely divided, severely disturbed spinels, separates, washes, dries and at temperatures below 1200 ° C, in particular between about 100 and 11.00 ° C, in the presence of oxygen, preferably air, heated.

This process makes it possible to obtain intimate, practically alkali-free mixtures of the various hydroxides or already finished, finely divided and severely disturbed spinels to produce which, after drying, can be achieved with a relatively mild thermal treatment, e.g. B. by annealing for about 1/2 hour at 800 to about 1100 ° C, can be converted into uniform, very well crystallized ferrites. This comparatively mild thermal treatment also allows annealing instead of in a pure sour. material atmosphere in air without a loss of oxygen which damages the properties of the ferrites occurs.

On divalent metal salts, which are used as starting materials for the process are suitable, for example: iron (TI), nickel, zinc, copper, Manganese, cobalt, cadmium and magnesium sulfate, chloride or nitrate.

As already mentioned, the should be added to the reaction mixtures Alloys according to the type and amount of their metal components to the metal ion mixture Solutions roughly correspond. Thus, for example, iron-nickel, iron-nickel-zinc or other iron alloys can be used. If necessary, the one or other metal component not in the form of an iron alloy component but rather be used as a metal in a mixture with iron or an iron alloy, so z. B. a mixture of an iron-nickel alloy with zinc.

In addition to oxygen, air and aromatic substances can be used as oxidizing agents Nitro compounds optionally -z. B. also chlorine, chlorates, perchlorates, manganates and chromates or bichromates can be used. Example 1 1 1 iron (II) chloride solution (20% Fe C12) and 26.2m1 of a cobalt (II) salt solution (13.43% Co) are mixed with 300 ml of 43.7 Ihigen sodium hydroxide solution were added. After that, a mixture of 41 one 0.5% iron (II) chloride and 3 ml of the above cobalt salt solution (13.43 1 / o Co) quickly admitted. The precipitate is obtained by introducing air (3 m3 / h) at 20 ° C. with stirring oxidized in about 2 hours. then are within 4 days at 60 ° C while stirring 200 g of a rasped Eiseri Käbält = alloy (96.0% Fe, 3.6% Co) added while. 1 m3 / h of air is continuously introduced. An olive-green one is obtained to orange-colored oxide hydrate with a- or, @, - Fe O Ö H structure. -The analysis of the at 100 °. C dried product shows about 83% Fe. O., 2.90 / 0 Co203 and 13; 6% Loss on ignition.

By gently heating (250 ° C) a strongly ferromagnetic, cobalt-containing spinel lattice of y-Fe. 03.

Example 2 150m1 of a 21% iron (II) sulfate solution in which 19.5 g Ni S 04 --- 7 H2 O are dissolved, 42 ml of a 19% sodium hydroxide solution are added and 25g of an -iron-nickel alloy (-2 / iFe and -, 1 /, Ni) and 100m1 nitrobenzene given. As the reduction takes place, another 225g of iron-nickel alloy is added and 165 ml of nitrobenzene were added. The resulting oxide hydrate precipitate becomes more common Way freed from aniline, slurried, washed and dried at 100 ° C.

The X-ray analysis of the product, dried at -100 ° C., shows fine particles Goethite structure with lattice defects, after 1/2 hour tempering at 800 ° C a finely divided Spinel lattice, after 1/2 hour annealing at 1100 ° a completely pure and coarsely crystalline Spinel lattice with clear a, a splitting of the last lines. Analysis: Fee 0, = 67.9%, Ni 0 = 29.7 0/0. Example 3 150m1 of a 21% iron (II) sulfate solution, in which 19.5 g Ni S O4 * 7 H2 O and 20.2 g Zn S O4 - 7H2 O are dissolved, are mixed with 42 ml of a 19% sodium hydroxide solution, 25 g of rasped iron-nickel alloy (-2 /, Fe and -1 /, Ni), 8 g of rasped zinc and 9.00m1 of nitrobenzene are added. In this scale, As the reduction proceeds, another 200 g of iron-nickel alloy, 66 g zinc and 165 ml nitrobenzene added; possibly still weak with H2 S 04 kept pissed off. After the reduction, the aniline is separated off in the usual way, the precipitate slurried, washed and dried at 100.degree. The accruing yellow-brown product shows an extraordinarily fine and severely disturbed spinel lattice with small parts of a goethite structure. After annealing at 800 ° C for 1/2 hour there is already a uniform and very well crystallized spinel lattice before. After annealing at 1100 ° C, the spinel lattice only changes insofar as the particle size continues to grow and the lines found at 800 ° C become even sharper and become less wide.

__ Analysis: Fe. 0, = 45.1%, Ni Q = 21.3%, __ Zn0 = 30.8%.

Claims (1)

Claim: Process for the production of ferrites by partial co-precipitation, characterized in that a mixed aqueous solution of iron (II) salts and salts of other suitable divalent metals is mixed with an alkaline precipitant which is insufficient for complete precipitation of the metal ions, the reaction mixture . an iron alloy corresponding in its composition to the metal ion mixture of the starting solution or a mixture of iron or an iron alloy with corresponding other metals and an oxidizing agent, preferably air or an aromatic nitro compound, in particular nitrobenzene, is added, the precipitate is separated off, washed out, dried and at temperatures below about 1200 ° C., in particular between about 100 and 1100 ° C., in the presence of oxygen, preferably air. heated. Documents considered: Swiss Patent No. 254931; French Patent Specification No. 1053 343rd; Zeitschrift für Schwingungs- und Schwachstromtechnik (Frequency), 1951, pp. 145 to 155, especially p. 14511.